The Role of Flare‐Driven Ionospheric Electron Density Changes on the Doppler Flash Observed by SuperDARN HF Radars

Chakraborty, Shibaji; Qian, Liying; Ruohoniemi, J. M.; Baker, J. B. H.; Mclnerney, Joseph M.; Watanabe, Midori

doi:10.1029/2021ja029300

Cited by 4 publications

(36 citation statements)

References 58 publications

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“…Distributions of the relative contributions from the change in ionospheric refractive index and the change in ray reflection height are statistically different (negligible overlap), with average contributions of ∼82% and ∼18%, respectively. This is consistent with the results from our previous single-event study of Chakraborty, Qian, et al (2021). 2.…”

Section: Discussionsupporting

confidence: 93%

“…Based on the maximum K p value of 2 + , on 5 May 2015 between 00 and 24 UT we conclude that the ionosphere was not perturbed by geomagnetic storm activity and thus this time period is suitable for observing the flare effects. We have chosen this event as a typical example in our case study paper (Chakraborty, Qian, et al, 2021) and use it here to demonstrate a data-model comparison. (Chakraborty, Qian, et al, 2021).…”

Section: Event Study: 5 May 2015mentioning

confidence: 99%

“…We have chosen this event as a typical example in our case study paper (Chakraborty, Qian, et al, 2021) and use it here to demonstrate a data-model comparison. (Chakraborty, Qian, et al, 2021). Additionally, the flare-driven reduction in the eastward electric field lessens the vertical 𝐴𝐴 ⃗ 𝐸𝐸 × ⃗ 𝐵𝐵 drift.…”

Section: Event Study: 5 May 2015mentioning

confidence: 99%

“…The top and bottom rows show statistics against one solar flare event (adapted from Chakraborty, Qian, et al, 2021) and multiple solar flare events (listed in Table 2), respectively. Against each radar event, we simulated data for Through statistical analysis of one event presented in Chakraborty, Qian, et al (2021), we demonstrated that, on average, (a) relative contributions to the Doppler flash from the change in refractive index and change in the ray reflection height are ∼82% and ∼18%, respectively; and (b) relative contributions of the D, E and F-regions are ∼21%, ∼31%, and ∼48%, respectively. In this statistical study, we find that the mean statistics did not change much, that is, on average, (a) relative contributions to the Doppler flash from the change in refractive index and change in the ray reflection height are ∼82% and ∼18%, respectively; and (b) relative contributions of D, E and F-regions are ∼21%, ∼33%, and ∼46%, respectively.…”

Section: Statistical Studymentioning

confidence: 99%

“…The flare‐enhanced electron densities at D, E, and F‐region altitudes produce a sudden change in the refractive index and a reduction in the eastward electric field. The change in refractive index alters the phase path length of the traveling radio wave which manifests as a Doppler blue the SuperDARN observations (Chakraborty, Qian, et al., 2021). Additionally, the flare‐driven reduction in the eastward electric field lessens the vertical

\vec{E}\times \vec{B}

drift.…”

Section: Modelsmentioning

confidence: 99%

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Driving Influences of the Doppler Flash Observed by SuperDARN HF Radars in Response to Solar Flares

et al. 2022

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Sudden enhancement in high‐frequency absorption is a well‐known impact of solar flare‐driven Short‐Wave Fadeout (SWF). Less understood, is a perturbation of the radio wave frequency as it traverses the ionosphere in the early stages of SWF, also known as the Doppler flash. Investigations have suggested two possible sources that might contribute to it’s manifestation: first, enhancements of plasma density in the D‐and lower E‐regions; second, the lowering of the F‐region reflection point. Our recent work investigated a solar flare event using first principles modeling and Super Dual Auroral Radar Network (SuperDARN) HF radar observations and found that change in the F‐region refractive index is the primary driver of the Doppler flash. This study analyzes multiple solar flare events observed across different SuperDARN HF radars to determine how flare characteristics, properties of the traveling radio wave, and geophysical conditions impact the Doppler flash. In addition, we use incoherent scatter radar data and first‐principles modeling to investigate physical mechanisms that drive the lowering of the F‐region reflection points. We found, (a) on average, the change in E‐ and F‐region refractive index is the primary driver of the Doppler flash, (b) solar zenith angle, ray’s elevation angle, operating frequency, and location of the solar flare on the solar disk can alter the ionospheric regions of maximum contribution to the Doppler flash, (c) increased ionospheric Hall and Pedersen conductance causes a reduction of the daytime eastward electric field, and consequently reduces the vertical ion‐drift in the lower and middle latitude ionosphere, which results in lowering of the F‐region ray reflection point.

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Section: Discussionsupporting

confidence: 93%

Section: Event Study: 5 May 2015mentioning

confidence: 99%

Section: Event Study: 5 May 2015mentioning

confidence: 99%

Section: Statistical Studymentioning

confidence: 99%

\vec{E}\times \vec{B}

drift.…”

Section: Modelsmentioning

confidence: 99%

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Driving Influences of the Doppler Flash Observed by SuperDARN HF Radars in Response to Solar Flares

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Geospace Concussion: Global Reversal of Ionospheric Vertical Plasma Drift in Response to a Sudden Commencement

Shi

Lin

Wang

et al. 2022

Geophysical Research Letters

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An interplanetary shock can abruptly compress the magnetosphere, excite magnetospheric waves and field‐aligned currents, and cause a ground magnetic response known as a sudden commencement (SC). However, the transient (<∼1 min) response of the ionosphere‐thermosphere system during an SC has been little studied due to limited temporal resolution in previous investigations. Here, we report observations of a global reversal of ionospheric vertical plasma motion during an SC on 24 October 2011 using ∼6 s resolution Super Dual Auroral Radar Network ground scatter data. The dayside ionosphere suddenly moved downward during the magnetospheric compression due to the SC, lasting for only ∼1 min before moving upward. By contrast, the post‐midnight ionosphere briefly moved upward then moved downward during the SC. Simulations with a coupled geospace model suggest that the reversed trueE⃗×B⃗ $\vec{E}\times \vec{B}$ vertical drift is caused by a global reversal of ionospheric zonal electric field induced by magnetospheric compression during the SC.

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Transient Response of Polar‐Cusp Ionosphere to an Interplanetary Shock

et al. 2023

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Geomagnetic field and plasma convection on Earth are strongly affected by interplanetary (IP) shocks and solar wind dynamic pressure pulses [P dyn ] (e.g., Boudouridis et al., 2007;Yue et al., 2010). After the IP shock hits the magnetosphere, the magnetopause moves inward, toward the Earth and the eastward magnetopause current intensifies rapidly as a result of this prompt compression (Araki, 1994). In consequence, the horizontal component of the geomagnetic field in low and mid-latitudes typically responds with an abrupt increase due to an enhanced eastward magnetopause current. This sudden increase in the horizontal component of the geomagnetic field on the dayside is referred to as an sudden impulse (SI) event with a precise onset time (Araki, 1994). In comparison with their clear stepwise signatures in the lower latitude regions, SI-associated geomagnetic disturbances at Abstract Interplanetary (IP) shock-driven sudden compression of the Earth's magnetosphere produces electromagnetic disturbances in the polar ionosphere. Several studies have examined the effects of IP shock on magnetosphere-ionosphere coupling systems using all-sky cameras and radars. In this study, we examine responses and drivers of the polar ionosphere following an IP shock compression on 16 June 2012. We observe the vertical drift and concurrent horizontal motion of the plasma. Observations from digisonde located at Antarctic Zhongshan station (ZHO) showed an ionospheric thick E region ionization and associated vertical downward plasma motion at F region. In addition, horizontal ionospheric convection reversals were observed on the Super Dual Auroral Radar Network ZHO and McMurdo radar observations. Findings suggest that the transient convective reversal breaks the original shear equilibrium, it is expected that the IP shock-induced electric field triggers an enhanced velocity shear mapping to the E region. The horizontal motion of the plasma was attributed to only the dusk-to-dawn electric field that existed during the preliminary phase of sudden impulse. We also found that ionospheric convection reversals were driven by a downward field-aligned current. The results of these observations reveal, for the first time, the immediate and direct cusp ionosphere response to the IP shock, which is critical for understanding the global response of the magnetosphere following an abrupt change in Interplanetory Magnetic Field (IMF) and solar wind conditions.Plain Language Summary On 16 June 2012, an interplanetary (IP) shock hit near-Earth space (geospace), resulting in enhanced plasma convection, auroral intensifications, and altering electric current systems in the high-and polar-latitude ionosphere. We present a case study characterizing the effect of IP shock-driven sudden impulse (SI) impact on geospace systems that changes vertical drift and horizontal convection observed by digital ionosonde and Super Dual Auroral Radar Network high-frequency radars. We found an SI-driven immediate vertical downward plasma motion, the sudden appearance of sp...

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The Role of Flare‐Driven Ionospheric Electron Density Changes on the Doppler Flash Observed by SuperDARN HF Radars

Cited by 4 publications

References 58 publications

Driving Influences of the Doppler Flash Observed by SuperDARN HF Radars in Response to Solar Flares

Driving Influences of the Doppler Flash Observed by SuperDARN HF Radars in Response to Solar Flares

Geospace Concussion: Global Reversal of Ionospheric Vertical Plasma Drift in Response to a Sudden Commencement

Transient Response of Polar‐Cusp Ionosphere to an Interplanetary Shock

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